net/http: use errors.As when checking for net.Error in Serve

[janisz]

What did you do?

go/src/net/http/server.go

Line 3045 in bdefb77

if ne, ok := err.(net.Error); ok && ne.Temporary() {

What did you expect to see?

var ne net.Error
if errors.As(err, &ne) && ne.Temporary() {

What did you see instead?

if ne, ok := err.(net.Error); ok && ne.Temporary() {

[seankhliao]

Is there any particular reason this should be checked with errors.As rather than a type assertion?

[ianlancetaylor]

Unless this solves a bug, let's leave the code alone to avoid churn. Thanks.

[janisz]

It's not a bug but it's surprisingly popular to copy and you can find this line in many repositories
https://sourcegraph.com/search?q=context:global+if+ne%2C+ok+:%3D+err.%28net.Error%29%3B+ok+%26%26+ne.Temporary%28%29+%7B+lang:go&patternType=literal

[davecheney]

That code isn’t incorrect; it’s asserting the error matches the net.Error interface. A more correct use of errors.As is to assert the error is a specific concrete type, which is not the case here.